Method for treating military equipment

ABSTRACT

Ferrous metal substrates, and in particular, military ammunition or armament, is rendered corrosion resistant by the application thereonto of a film-forming composition consisting essentially of an organic solvent having a maximum flash point of about 150*F. and a calcium soap of a mixture of organic acids, lactones and esters. When the composition dries on the substrate, a camouflaging olive drab color is imparted thereto.

United States Patent [191 Otrhalek et al.

[ METHOD FOR TREATING MILITARY EQUIPMENT [75] Inventors: Joseph V. Otrhalek, Dearborn;

Russell S. Banush, Trenton, both of Mich.

[73] Assignee: Basf Wyandotte Corporation,

Wyandotte, Mich.

[22] Filed: Jan. 20, 1972 [21] Appl. No.: 219,516

[52] US. Cl. 148/6.15 Z, 117/89, 117/134 [51] Int. Cl. C23f 7/10 [58] Field of Search252/39, 389; 148/615 R, 6.15 Z;

[56] References Cited UNITED STATES PATENTS 2,588,234 3/1952 Henricks l48/6.l5 Z

[451 Feb. 12,1974

2,662,836 12/1953 Montgomery et al. 1 17/134 X 2,779,737 l/l957 Koft et a1 252/39 2,895,978 7/1959 3,380,859 4/1968 Dell l48/6.l5 Z

Primary Examiner-Ralph S. Kendall Attorney, Agent, or FirmRobert M. Phipps; Joseph D. Michaels; Bernhard R. Swick [57] ABSTRACT 3 Claims, No Drawings BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ferrous metal surface corrosion inhibition and in particular to method and composition for rendering ferrous metal surfaces, especially military ammunition or armaments, corrosion resistant and with suitable camouflage.

2. Prior Art The art of metal finishing, and in particular the field of art relating to corrosion inhibition of ferrous products, has given rise to a wealth of technology in regard thereto. Most prevalent within the presently practiced methods for finishing ferrous metal surfaces is a zinc phosphating treatment to passivate the surface. In

order to render a zinc phosphated ferrous metal surface corrosion resistant the prior art has also taught the subsequent application to the passivated surface of a water-insoluble coating, such as, paint, oil, or wateremulsifiable oil. Oils are adequate replacements for paints except where a high degree of corrosion resistance is required.

One particular area where paint has heretofore been required is military ammunition or armaments, such as, cannon shells, bazookas, and the like. Paint has been utilized not only because of corrosion resistance but most importantly the ability of paint to camouflage the war head. However, paint creates certain problems in this area, and in particular with regard to paint burnoff within the barrel of the military hardware, thus, necessitating cleaning of the barrel prior to refiring thereby reducing efficiency.

The present invention seeks to improve upon this prior art by providing an oil-based finish for zinc phosphated ammunition which eliminates the problem of burn-off and which simultaneously camouflages the warhead.

SUMMARY OF THE INVENTION In accordance with the present invention, ferrous metal military ammunition and other equipment is rendered corrosion resistant and olive drab in color, i.e., camouflaged, by a process which generally comprises:

a. zinc phosphating the equipment,

b. applying to the phosphated equipment a filmforming mixture of an organic solvent having a maximum flash point of about 150 F. and a calcium soap of a mixture of organic acids, esters and lactones, and

c. removing the solvent to deposit a camouflaging corrosion inhibiting film on the equipment.

For a more comprehensive discussion of the present invention, reference is made to the following detailed description and examples.

DESCRIPTION OF THE PREFERRED EMBODIMENT It has been found that when ferrous metal military ammunition and other military equipment is treated in accordance with the present invention, the ammunition is thereby rendered corrosion resistant and has a camouflaging color, i.e., olive drab, imparted thereto. Moreover, the problem of paint bum-off heretofore associated with painted ammunition during discharge or firing, is hereby eliminated.

By the term ferrous metal, as used herein, is meant iron, wrought iron, and iron-carbon alloys, i.e., steel.

According to the present process, ferrous metal am munition is rendered corrosion resistant and with a camouflaging color by zinc phosphating the ammunition, applying to the zinc-phosphated article a filmforming mixture of an organic solvent having a maximum flash point of about 150 F. and a calcium soap of a mixture of organic acids, esters and lactones, and then removing the solvent to form a film thereon.

The zinc phosphating step of the present process can be achieved in accordance herewith by any conventional zinc phosphating technique. Generally, the step of zinc phosphating a ferrous metal surface comprises applying an aqueous zinc phosphating solution to a clean ferrous metal surface by immersion, spraying or the like, generally at a temperature ranging from about to 200 F. for a period of time ranging from about 5 to 30 minutes.

Typical zinc phosphating baths or solutions generally comprise a dilute aqueous solution of zinc, phosphate,

hydrogen and nitrate ions. Other ions are generally included in the zinc phosphating solution to accelerate the reaction or modify the coating. Such other ions are, for example, nickel, fluoride, chlorate, nitrite, or mixtures thereof. These zinc phosphating solutions are well-known to those skilled in the art and any conventional prior art zinc phosphating process and/or solution can be advantageously employed in the practice of the'present invention.

After the ammunition is zinc phosphated, it is usually water rinsed and dried. Optionally, after water rinsing, and prior to drying, the zinc phosphated ammunition may be further treated with a dilute aqueous solution of chromic and phosphoric acid. Again these procedural steps are well known to the skilled artisan.

- The second step of the process generally comprises applying onto the zinc phosphated surface a filmforming mixture of an organic solvent having a maximum flash point of about 150 F. and the calcium soap of a mixture of organic acids, esters and lactones. The film-forming mixture consists essentially of from about 40 to by weight of organic solvent and from about 20 to 60% by weight of the calcium soap mixture. Preferably, the film-forming mixture consists essentially of from about 50 to 75% by weight of organic solvent and from 25 to 50% by weight of the calcium soap mixture.

Useful organic solvents having a maximum flash point of about F. include for example, naphtha, including V.M.P. naphtha, and the like, mineral spirits, aromaticpetroleum distillate cut solvents, kerosene, benzene, toluene, xylene, hexane, heptane, and the like, as well as mixtures thereof. The preferred solvent is naphtha.

The calcium soaps used herein are generally derived from the oxidation of petroleum, the oxidation of petroleum providing organic acids, esters and lactones, this oxidation mixture is then used to form the calcium soap thereof by reaction with calcium oxide. A suitable commercially available calcium soap mixture of the hereinabove described type is sold under the name ALOX 2140 by Alox Corporation. ALOX 2140 is a highly viscous, dark brown substance. Some of the typical physical and chemical properties of ALOX 2140 are as follows:

Melting point, ASTM Dl27-63 28 F. min. Needle Penetration, ASTM D1321-61T 60 max. Specific Gravity, ASTM D7l-52 77F. 0.94 Weight per Gallon 77 F. 7.8 lb.

The film-forming mixture of solvent and calcium soaps can be prepared by any conventional method under ambient conditions by mixing the two ingredients together.

The film-forming mixture is applied to the zinc phosphated ammunition surface by any conventional method such as brushing, spraying, immersing or the like and at atmospheric pressures and temperatures ranging from about room temperature to upwards of about 175 F. Generally, a sufficient amount of the mixture is applied to the ammunition to provide a final film thickness of from about 0.25 to 1.5 mils, preferaammunition an olive drab colored film which effectively inhibits corrosion on the ammunition, this film not being subject to burn-off when the ammunition is discharged. No subsequent treatment of the ammunition is required.

Although the present invention has been described with reference to ammunition, it is to be understood that it is also equally applicable to other military equipment, which requires camouflaging and corrosion resistance such as, vehicles, and the like.

For a more complete understanding of the present invention, reference is made to the following examples which are not to be construed as limitative of the invention. In the examples all parts are by weight, absent indications to the contrary.

EXAMPLE I This example illustrates the preparation of corrosion resistant, camouflaged ammunition in accordance with the present invention.

A 105 mm steel shell is cleaned by immersing the shell for about minutes in a caustic solution maintained at about 170 to 180 F. The caustic bath consists of, by weight, 2% caustic soda; 2% soda ash; 0.9% sodium metasilicate; 0.8% sodium tripolyphosphate; 0.3% sodium lignin sulfonate; 0.1% sodium glueonate; 0.6% sodium linear alkylate sulfonate and 93.3% water.

After cleaning, the shell is then rinsed with water to remove any residuals of the caustic solution.

The shell is then zinc phosphated by immersing the shell in a zinc phosphating solution maintained at about 150 to 165 F. for about 10 minutes. The zinc phosphating solution used herein consists essentially of, by weight, 0.8% zinc ions, 2.4% phosphate ions, 0.07% nickel ions, 0.6% nitrate ions and 0.3% ferrous ions. The shell is then removed from the solution,

rinsed with water at a temperature of about 130 F. to promote dry off, and dried with a forced air drier at 300 F. The zinc phosphated shell is next immersed for about one minute in a mixture of by weight of naphtha and 30% ALOX 2140. The shell is removed therefrom and forced air dried at'300 F. The sotreated shell has an olive drab color.

EXAMPLE II The procedure of Example I is repeated with a mm shell but using a different conventional zinc phosphating solution and a different film-forming mixture.

- The zinc phosphating solution consists essentially of, by weight, 0.2% zinc ions, 0.6% phosphate ions, 0.01% nickel ions, 0.125% nitrate ions, and 0.05% nitrite ions. The shell is immersed in this solution, which is maintained at about to F., for about five minutes.

The film-forming mixture, used herein, consists essentially of 60% by weight of toluene and 40% by weight ALOX 2140. The film-forming mixture, in this instance, is sprayed onto the zinc phosphated shell.

The so-treated shell is drab olive in color.

EXAMPLE III EXAMPLE IV The procedure of Example 111 is repeated except that the zinc phosphated shell is sprayed at about 135 F. for sixty seconds with a chromic acid-phosphoric acid aqueous solution identical to the one employed in Example III. In this example, the film-forming mixture consists of about 74% by weight of an aromatic hydrocarbon solvent which is a petroleum distillate cut having a distillation range of 188 to 210 C. and which is sold by Enco Chemical under the name ENCO 150, and about 26% by weight of ALOX 2140.

EXAMPLE V Using a film-forming mixture as described in Example IV, a series of 1010 steel panels are zincphosphated, then the film-forming mixture is applied and dried to form an olive drab film on the panels.

Thereafter, the so-treated panels are subjected to a continuous salt spray for 120 hours. After the 120 hours have elapsed there is still no evidence of corrosion. This is contrasted with the current military specifications on corrosion requirements for ammunition,

TT-C-490A, which requires 48 hours of salt spray exposure in order to qualify thereunder.

Outdoor exposure tests on 105 mm shells treated similarly to the steel panels evidenced no corrosion even after six months.

Having thus described the invention, what it is de- 0. removing the solvent from the film-forming mixsired to claim and secure by Letters Patent is: ture to deposit a film on the equipment, the film 1. A method for treating ferrous metal military rendering the equipment corrosion resistant and equipment which comprises: with a camouflaging olive drab color.

a. zinc phosphating the equipment, 5 2. The method of claim 1 wherein the calcium soap b. applying to the zinc phosphated equipment a filmmixture has the following physical properties:

forming mixture consisting essentially of 1) from Melting point 28 F. min. about 40 to 80% by weight of an organic solvent Needle Penetration 60 max. having a maximum flash point of about 150 F., Specific gravity at 77 F. 0.94 and (2) from about to 60% by weight of a cal- 10 Weight per gallon at 77 F. 7.8 lbs. cium soap of a mixture of organic acids, esters and 3. The method of claim 2 wherein the solvent is lactones the organic acids, esters and lactones naphtha.

being derived from the oxidation of petroleum, 

2. The method of claim 1 wherein the calcium soap mixture has the following physical properties: Melting point - 28* F. min. Needle Penetration - 60 max. Specific gravity at 77* F. - 0.94 Weight per gallon at 77* F. - 7.8 lbs.
 3. The method of claim 2 wherein the solvent is naphtha. 